Material handling vehicles are commonly found in warehouses, factories, shipping yards, and, generally, wherever pallets, large packages, or loads of goods are required to be transported from place to place. Material handling vehicles typically include load bearing forks for lifting packages or pallets for transporting, a drive motor for propelling the truck, a steering control mechanism, and a brake.
A common energy source for electrically based material handling equipment is a Lead Acid Battery (LAB). LABs are robust and have historically been inexpensive, but a drawback to such batteries is that a lead acid battery may not provide the desired power needs of modern heavy use material handling vehicles. Although LABs have traditionally been more cost effective than alternative energy sources, improvements in the field of alternative energy source technology have led to lower costs and fewer environmental concerns for new alternative energy sources. Furthermore, concerns with LABs, such as difficulties encountered when charging or rapidly recharging these batteries without damaging them, have also led to a desire for new energy sources to be used by industrial material handling vehicles.
New alternative energy sources, such as fuel cells or Lithium Ion Batteries (LIBs), can be completely recharged or charged with high currents in less time than lead acid batteries with little or no damage. However, an important advantage that LABs have is that most existing material handling vehicles are designed to work with the voltage declines of LABs. Such material handling vehicle designs are typically not compatible with how LIBs or fuel cells behave. For example, LIBs or fuel cells may automatically disconnect, or may not be able to handle typical current draws, for example, at very low temperatures. These considerations make it unpractical to simply plug in a new energy source to a material handling vehicle and run the material handling vehicle until a power cutout.
Another important consideration is that most material handling vehicle computer systems are not programmed to address the limits of new energy sources before a power cutout occurs. Typically, the TCS for existing material handling vehicles will shut down functions, such as Lift, to indicate to maintenance personnel to service the LAB. This function is based on sensing a voltage drop that does not occur with a LIB or other new energy sources. When using a LAB, vehicle performance will decline as the LAB State of Charge declines, but a LAB will not suddenly shut down the vehicle while it is in operation. New energy sources, such as a LIB or a Fuel Cell, must shut down operation for protection of the energy source.
Furthermore, extending operation hours of the material handling vehicle using a new energy source can potentially result in damage to the energy source. For instance, LIBs may brick. Bricking occurs when a LIB's charge is reduced to near 0% State of Charge and any cell of the LIB is pulled below the minimum voltage limit. Thus, the energy source could be permanently damaged. Operating a LAB to 0% battery state of charge does shorten the battery life, but unlike with LIBs, a LAB can recover from such an event.
Importantly, there is currently no standardized way for a material handling vehicle to detect what type of power source is being utilized or for the material handling vehicle to adjust its behavior to the limits of that power source, or to adjust its behavior to handle an indication of battery energy depletion, or to communicate or record the status or specific data (for example fault codes) from that power source. Many current material handling vehicle designs assume that the power source will behave like a LAB.
Therefore, it is desirable to provide a public standard interface for communication between the Truck Control System and the energy source control system, which is typically called a Battery Management System.